There is an increasing demand for patterned deposition of materials on receivers in traditional image and document printing and upcoming manufacturing applications. These deposition techniques can be broadly classified in non-contact printing methods such as ink jet printing and contact printing methods such as screen printing, flexography, offset lithography, or slot coating.
Ink jet printing has become recognized as a prominent contender in the digitally controlled, electronic printing arena because, e.g., of its non-impact, low-noise characteristics, its use of plain paper and its avoidance of toner transfer and fixing that is required in electrophotography based printing methods. Traditionally, inkjet printing is accomplished by one of two technologies referred to as “drop-on-demand” and “continuous” inkjet printing. In both, liquid, such as ink, is fed through channels formed in a printhead. Each channel includes a nozzle from which droplets are selectively extruded and deposited upon a recording surface.
The first technology, “drop-on-demand” (DOD) ink jet printing, provides ink drops that impact upon a recording surface using a pressurization actuator, for example, a thermal, piezoelectric, or electrostatic actuator. One commonly practiced drop-on-demand technology uses thermal actuation to eject ink drops from a nozzle. A heater, located at or near the nozzle, heats the ink sufficiently to boil, forming a vapor bubble that creates enough internal pressure to eject an ink drop. This form of inkjet is commonly termed “thermal ink jet (TIJ).”
The second technology commonly referred to as “continuous” ink jet (CIJ) printing, uses a pressurized ink source to produce a continuous liquid jet stream of ink by forcing ink, under pressure, through a nozzle. The stream of ink is perturbed using a drop formation mechanism such that the liquid jet breaks up into drops of ink in a predictable manner. One continuous printing technology uses thermal stimulation of the liquid jet to form drops that eventually become print drops and non-print drops. Printing occurs by selectively deflecting one of the print drops and the non-print drops and catching the non-print drops. Various approaches for selectively deflecting drops have been developed including electrostatic deflection, air deflection, and thermal deflection.
Printing systems that combine aspects of drop on demand printing and continuous printing are also known. These systems offer increased drop ejection frequency when compared to drop on demand printing systems without the complexity of continuous printing systems.
Many other applications are emerging in which it is desired to dispense liquids, other than inks, that need to be finely metered and deposited with precision. It would be advantageous to dispense these liquids using devices similar to inkjet printheads. Often, however, these liquids have one or more characteristics, for example, a high viscosity or a high particle loading, which makes it impractical or extremely difficult for these liquids to be deposited using devices similar to inkjet printheads. Other examples include inks are sensitive to heat making it incompatible with a bubble actuator and inks including solvents that easily dry and adhere to the nozzle structure causing a failure of the printhead. As such, there is an ongoing effort to find devices and techniques that are suitable for dispensing these liquids.